This invention relates to a current detector for detection or measurement of electric current flowing in an electric circuit, and more specifically to such a detector incorporating a Hall-effect device more generally known also as Hall generator.
The Hall generator is built upon the familiar Hall effect to develop a voltage, known as Hall voltage, in proportion to the strength of the magnetic field applied. The Hall generator therefore lends itself to use as a magnetism detector. Additionally, positioned contiguous to a path of electric current, the Hall generator will put out a voltage indicative of the magnitude of the current by being acted upon by the magnetic field appearing in proportion to the current magnitude. The closer the Hall generator is positioned to the current path, the higher will be its sensitivity of current detection.
The instant applicant proposed in Japanese Unexamined Patent Publication No. 2000-174357 a current detector employing a Hal generator. This prior art device was designed explicitly for high detection sensitivity. To this end a current-path conductor layer for the flow of electric current to be detected was laid, via an insulating film, over a semiconductor substrate having a Hall generator formed therein. The prior art device has later proved to be still not totally satisfactory in sensitivity, in noise immunity, in the magnitude of current that can be detected or measured, and in the cost of manufacture.
The present invention aims at improvement of the sensitivity of the current detector of the kind defined.
Another object of the invention is to improve the noise immunity of the current detector of the kind defined.
Still another object of the invention is to accomplish the foregoing objects in detecting current of much greater magnitude than has so far been possible with the noted prior art with a minimum of performance fluctuations.
Stated in brief, the invention concerns a current detector utilizing the Hall-effect for detection or measurement of electric current, comprising a current-path conductor for carrying current to be detected or measured, a Hall generator disposed opposite the current-path conductor for generating a Hall voltage proportional to the strength of a magnetic field due to the current flowing through the current-path conductor, and a casing of electrically insulating material holding the current-path conductor and the Hall generator in prescribed relative positions. The invention particularly features magnetic layer means disposed opposite the current-path conductor via the Hall generator.
In the preferred embodiments of the invention to be disclosed subsequently, a layer of magnetic material such as a sheet of Permalloy is held against the Hall generator and enveloped in the casing for improvements in immunity to external magnetic or electromagnetic disturbances and in sensitivity to the magnetic field due to the current flowing through the current-path conductor. Additionally, the casing is itself enclosed in a covering of Permalloy or like material. Experiment has proved that such magnetic layer means make substantive contributions toward the higher sensitivity of the current detector, presumably by lessening magnetic resistance to the flux through the Hall generator and by preventing the flux from unnecessarily spreading. Improvements have also been observed in immunity to external magnetic and electromagnetic disturbances.
It is also preferred that the Hall generator, fabricated in the form of a semiconductor chip, be bonded to a metal-made mounting plate via the magnetic layer of Permalloy or the like on the one hand and, on the other hand, held opposite the current-path conductor in very close proximity thereof. This arrangement has proved most conductive to improved sensitivity through reduction of magnetic resistance to the flux acting on the Hall generator
The current-path conductor of the current detector according to the invention should preferably be a piece of sheet metal that is slit to provide a U-shaped current path around the Hall generator. The sheet-metal current-path conductor is integrally united with the Hall generator by a casing of plastics or like insulating material. The current detector of this construction is capable of handling current of 100 to 600 amperes.
The above and other objects, features and advantages of this invention will become more apparent, and the invention itself will best be understood, from a study of the following description and appended claims, with reference had to the attached drawings showing the preferred embodiments of the invention.